Question: I want input on the best way to help out my little girl. Any ideas are welcome!

I have twins that are in 3rd grade, one of them is great in school, the other one... well she tries. Her handwriting is not the best, her spelling... I try to help her by having her open the kids dictionary and writing down 15 words every day, but it's not helping much. I am starting to worry that she won't pass and her sister will. To top off everything we have to move, and her dad and I are getting a divorce. I just worry about her and making it through school. She is a very shy, quiet, sweet kid. I just want to know the best way to help her out.